How can I consume a api-rest service by sending it a pdf file c#

Question

I am trying to consume an api-rest method post https://server/upload, receives 3 parameters: file: directory: subdirectory: enter image description here

How can I consume this api-rest from a mvc web application

<form action="UploadPost" method="post" enctype="multipart/form-data">
    <input type="text" name="directory" value="" />
    <imput type="text" name="subdirectory" value=""/>
    <input type="file" name="file"/>
    <button class="btn-danger" type="submit">Upload</button>
</form>

private void UploadPost(string dir, string subdir)
{
    var url = $"https://server/upload";
    var request = (HttpWebRequest)WebRequest.Create(url);
    string json = $"{{\"data\":\"{dir, subdir}\"}}";
    //
    request.Method = "POST";
    request.ContentType = "application/json";
    request.Accept = "application/json";
    using (var streamWriter = new StreamWriter(request.GetRequestStream()))
    {
        streamWriter.Write(json);
        streamWriter.Flush();
        streamWriter.Close();
    }
    try
    {
        using (WebResponse response = request.GetResponse())
        {
            using (Stream strReader = response.GetResponseStream())
            {
                if (strReader == null) return;
                using (StreamReader objReader = new StreamReader(strReader))
                {
                    string responseBody = objReader.ReadToEnd();

                    Console.WriteLine(responseBody);
                }
            }
        }
    }
    catch (Exception ex)
    {
        log.Error(ex);
    }
}

your help please. Thank you so much